General usage:
* The enclosure around the garden was made of white picket fence.
* The zookeepers placed the lion in a special enclosure for its safety.
* The enclosure of the letter was a bit cryptic, but I think I understand the message.
Figurative usage:
* The city felt like an enclosure of concrete and steel, far from the open spaces of nature.
* His love for her was a comforting enclosure, shielding him from the harsh realities of the world.
* The silence of the library was an enclosure of peace and quiet, allowing him to concentrate on his studies.
Specific contexts:
* The enclosure on the back of the book contained a map and glossary.
* The enclosure of the document contained the company's financial statements.
The best way to use "enclosure" depends on the context and the specific meaning you want to convey.